This project focuses on nonhuman primate vocal communication and its biological and evolutionary relationships to cognition and social behavior. In recent years there has been increased appreciation of the importance of vocal communication in the social lives of nonhuman primates and a goal of the current research is greater understanding of complexity in the vocal signals of monkeys. Studies have indicated signals can represent objects and events in the external world (i.e., have the property of external reference) such findings raise the possibility that animal communication might share the denotative context independence of human language symbols. A complicating issue in efforts to categorize the primate world reflected in communication is that researchers have approached the problem as though the animals classify items with a logic system in which there are only two truth values, 1 or 0 (true and false). Although studies have established associations between differen t vocalizations and referents using this simple dichotomy, it is likely that such bivalent logic is not the actual basis for the categorization of many things communicated about by monkeys. Our research supports this prediction and suggests that a multi-valued or fuzzy logic system, one with more than two truth values, might provide a more realistic way to conceptualize the categorization of certain referents of monkey vocalizations. However, emotional and motivational referents of calls are also indicated in certain vocalizations such as adult copulation calls and the distress cries of infants. As more is learned about how nonhuman primates classify both their physical and social worlds through study of their communication systems, the knowledge gained can be employed in the design of experiments that explore critical cognitive and emotional dimensions of primate behavior relevant to understanding the evolutionary history of our own species. FUNDING Yerkes $20,000 1/01/98 - 12/31/98 PUBLICATIONS Gouzoules, H., Gouzoules, S. and Tomaszycki, M. Agonistic screams and the classification of dominance relationships are monkeys fuzzy logicians? Animal Behaviour 55:51-60, 1998. Gouzoules, H., Gust, D.A., Donaghey, B. and St. Andre, E. Estrus vocalizations in two primate species (Cercocebus torquatus atys and Macaca nemestrina) evidence for an effect of intrasexual competition. Evolution of Communication (In press). Maestripieri, D., Jovanovic, T.J. and Gouzoules, H. Crying and infant abuse in rhesus monkeys. Child Development (In press). P51RR00165-38 1/1/98 - 12/31/98 Yerkes Regional Primate Research Center